On Wed, Jan 11, 2017 at 12:02:40PM -0600, Segher Boessenkool wrote:
> On Thu, Jan 05, 2017 at 05:46:51PM +0100, Dominik Vogt wrote:
> > The attached patch deals with another type of zero_extend that is
> > not yet handled in change_zero_ext, i.e. (zero_extend
> > (pseudoreg)), without a "subreg" in between. What do you think?
> > (Mostly untested yet.)
>
> My main question is: where is this useful? Can you show some example
> please?
With this test program:
int foo (int *b)
{
int i;
int r;
for (i = 0; i < 77; i++)
{
r |= b[0] > 0;
r |= b[i] > 0;
}
return r;
}
before combine we have
(insn 47 45 48 7 (set (reg:SI 104)
(zero_extend:SI (reg:QI 103)))
(insn 48 47 49 7 (parallel [
(set (reg/v:SI 88 [ r ])
(ior:SI (reg/v:SI 88 [ r ])
(reg:SI 104)))
(clobber (reg:CC 33 %cc))
])
combine tries
(set (reg/v:SI 88 [ r ])
(ior:SI (zero_extend:SI (reg:QI 103))
(reg/v:SI 88 [ r ])))
With the patch it also tries
(set (reg/v:SI 88 [ r ])
(ior:SI (and:SI (subreg:SI (reg:QI 103) 0)
(const_int -1 [0xffffffffffffffff]))
(reg/v:SI 88 [ r ])))
which is just one of the standard patterns for rosbg.
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
